1. Field of the Invention
This invention relates to the field of microprocessors and, more particularly, to methodologies for developing microprocessors.
2. Description of the Related Art
Advances in microprocessor performance have been in large part responsible for major advances in the functionality and capability of personal computer (PC) systems. As a historical rule of thumb, microprocessor performance has doubled every 18 months since the introduction of the first microprocessors in the late 1970's. While the continued increase in microprocessor performance has resulted in many benefits for PC system users, the rapid pace of change underlying the increasing performance has created problems for microprocessor designers.
The rapid increase in performance of microprocessors may lead to a required reduced design cycle for microprocessor designs (i.e. the time from initiation of a project to shipping a product resulting from the project). Since a particular product may exhibit obsolete performance in as few as 18 months, new products with substantially improved performance must be introduced frequently. Additionally, the substantial improvement in performance needed to be competitive in the new products generally requires significant design changes to previous products and often requires a complete redesign.
Advances in semiconductor fabrication technology have fueled the growth in microprocessor performance. As the feature sizes of transistors have steadily decreased, higher frequency operation has resulted from the more rapid switching times and the reduced capacitive load exhibited by the smaller transistors. Additionally, the reduction in feature sizes has lead to an increase in the number of transistors which may profitably be included upon a given semiconductor chip. Die size (i.e. chip area) is limited by yield concerns and other cost-related concerns associated with the manufacture of high volume microprocessors. However, with the reduction in feature size, more transistors may be incorporated upon the relatively fixed die size.
Unfortunately, the increase in the number of available transistors may directly correlate to an increase in design complexity for the microprocessor. This increase in complexity coupled with the above-mentioned reduced cycle times enormously increase demands upon microprocessor designers. The increased complexity leads to an increase in the amount of verification required (e.g. the number and complexity of test vectors needed to verify the design). Additionally, the layout and circuit design tasks may be increased due to the larger number of transistors incorporated into the design. Still further, qualification data indicating that the microprocessor can be profitably manufactured in high volumes must be generated. A methodology for designing microprocessors which alleviates this demand is therefore desired.